DNA topoisomerase II ?: Stability and distribution in different animal cells in comparison to DNA topoisomerase I and II ?

DNA topoisomerase I and the isoforms ? and ? of DNA topoisomerase II were analyzed in different animal cells using a panel of monoclonal antibodies (MoAbs). The ? isoform is a most unstable enzyme. We investigated conditions to stabilize ? isoform because its variability changes according to the derivation of cells. We describe two MoAbs specific to DNA topoisomerase I: the first one recognizes the enzyme in all the species tested including fish; the second one, in contrast, recognizes an epitope present only in mammalian cells. We also found that eight of eight MoAbs against DNA topoisomerase II ? and five of six against the ? isoform recognize the respective enzymes in all the species tested excluding fish. In addition, MoAbs to the ? isoform are specific to epitopes not present in the carboxyl third of the enzyme. © 1993 Academic Press, Inc.